Although primary malignant brain tumors constitute only 2 percent of all cancers, they are associated with severe disability and a high risk of death. Gliomas comprise 50 percent of all primary brain tumors in adults. These high-grade, malignant tumors grow rapidly and are associated with a poor prognosis. This study is part of continuing efforts to develop more effective therapeutic regimens. The objectives are 1) to determine the activity and toxicity of topotecan in the treatment of adults with progressive, persistent or recurrent malignant glioma, 2) to measure the topotecan pharmacokinetics and topoisomerase I levels in tumor samples and correlate these values with the response, and 3) to measure in vitro sensitivity of individual sample topoisomerase I to topotecan and to determine the association of tumor response to topoisomerase sensitivity. This study has just begun patient accession.